> Gudgeon brothers did this a few years ago. Copies of it were posted here.
> The results were as you would expect, heavier layups of cloth being
> stronger then thinner layups. Nick may still have copies of this
> information around (and probably will not charge you for providing it). At
> the worse, contact West systems for a copy of it. In fact, they probably
> have it on their web page.

I don't think the info is on their web page, but they did publish results from panel tests in the Winter 98 (#10) issue of Epoxyworks. They tested 12"x12" cedarstrip and plywood panels with various glass schedules. Three point bending loads were applied parallel to the grain of the cedar on the strip panels and parallel to the face grain on the plywood panels. Some of the results (for 1/4" cedar strip panels):

glass/wood/glass | panel weight (oz) | deflection (in) | failure (lbs)

4oz/1/4"/4oz | 9.0 | 0.45 | 150

4oz/4oz/1/4"/4oz/4oz | 10.3 | 0.70 | 375

6oz/1/4"/6oz | 9.8 | 0.49 | 221

6oz/6oz/1/4"/6oz/6oz | 12.3 | 0.58 | 450

As expected, heavier layups produced stronger panels. Also, there was relatively little weight gain in relation to the increase in panel strength. For the 6oz layup, a double layer of glass results in a panel that is approximately 25% heavier but supports a 104% higher load - twice as strong is not twice as heavy.

But ..... did they build the panels right? (Sorry - I couldn't resist)

Michael :o)